The present invention relates in general to synthetic material closures for use in providing an internally threaded opening in a container end. More particularly, the present invention relates to the use of a portion of the container (drum) end as a back-up support for the closure (1) during the crimping operation locking the closure into the container end and (2) thereafter as the closure is subjected to various stresses.
The concept of providing a plug or a closure in combination with a metal container end is disclosed in a number of prior references. In some cases, the closure is internally threaded and in some cases the closure is fabricated out of a synthetic material, such as plastic. In the majority of these prior references, the drum end is formed with a raised and circular boss, of varying configurations, which is utilized for securing or anchoring the closure in place. In some of these prior references, the closure orientation may be of concern and in others, additional components are necessitated in order to complete the assembly.
Some examples of these foregoing types of closures and closure/drum combinations are provided by the following patent references and to that degree these references are relevant to the present invention.
______________________________________ U.S. Pat. No. Patentee ______________________________________ 4,195,750 Fee 4,135,639 Dillon 4,316,318 Mineo 4,231,488 Ward 4,252,246 Johnson 4,087,019 Yamazaki 4,418,832 Schneider 4,164,304 Roberson 4,114,779 Stoll, III 4,109,600 Post 4,078,696 Crisci ______________________________________
Fee discloses a flange for a container opening which has an internally threaded aperture to receive a plug, and a plurality of external serrations in a circularly spaced-apart relationship around the periphery of the upper portion of the flange. A container suitable for the flange has a boss around the container opening in a wall (usually the end wall) of the container and the boss is formed with internal serrations equal in number to the number of external serrations on the flange. The plug is removable from the flange when access to the contents of the container is desired.
Dillon discloses a closure construction for a container, such as a steel drum, which includes a flange member having an internally threaded opening adapted to be closed by an externally threaded cap. The flange member includes an integral flange portion that is firmly secured in an offset portion of the container wall by means of spaced protuberances at the outer edge of the flange portion that are tightly engaged by the offset portion of the container wall.
Mineo discloses a method of mounting a mouthpiece onto a container which comprises fitting a tubular mouthpiece having an externally threaded portion and an annular leg portion of reduced thickness at the lower portion of the externally threaded portion, around an upright tubular portion formed integral with the top plate of the container, bending the upper end of the tubular portion outward to cause the bent edge of the upper end to hold the upper end of the mouthpiece from above and pressing outward from inside the lower end of the tubular portion to form a plurality of projections at the lower end of the tubular portion.
Ward discloses a container closure spout construction for incorporation into a metal drum container and including a container wall portion having a spout aperture, and a closure spout member having a peripheral substantially transversely extending flange portion and, preferably integral therewith, an intermediate substantially axially extending tubular portion defining a closure spout opening within the flange portion and adapted to removably receive a cooperating closure element such as a plug or cap.
Johnson discloses a fuel tank cap assembly which includes a closure, a cover, and a skirt. Each of these component parts is of an injection-molded construction with the cover and skirt having interlocking portions which cooperate to maintain the cap assembled with a portion of the closure secured between the cover and the skirt.
Yamazaki discloses a two-part plug arrangement for a container which includes an outer plug of soft resilient material and a mating inner plug of deformable material. The inner plug is seated within the outer plug, and the mating plugs are together seated within an opening of a wall of the container. Such opening has an annular turn-over wall along its circumference, and the outer plug has an annular flange adapted to engage such turn-over wall.
Schneider discloses a container which is provided with an annular support flange which can be flat or rise inward in a frustum-defining manner. The flange is connected to the container contents-containing base portion in the vicinity of the lower edge of the cover when in the seated position. The support flange is used for supporting the fingers during removal of the cover.
Roberson discloses a drum having a blow-molded liner wherein the liner has a neck which extends through an opening formed in a wall of the drum. The closure assembly is provided for association with the neck both to retain the neck relative to the drum and to close the neck. The closure assembly includes a retainer and a closure member, the retainer including inner and outer concentric walls joined in spaced relation by a bridging portion. The neck is threadedly engaged with the outer wall and is received between the two walls with a terminal portion of the neck being wedgedly formed to assure a seal between the retainer and the neck.
Stoll III discloses an improved closure assembly for plastic drums which includes female buttress threads formed on a tubular projection of the drum head and an adaptor inserted into the tubular projection threadedly engaging the buttress threads. The adaptor includes internal standard pipe threads which are adapted to receive standard pipe-threaded members, such as dispensing valves, pump fittings, as well as standard bung plugs. Means are also provided for sealingly isolating the buttress thread inter-engagement to prevent product accumulation therebetween.
Post discloses a process of applying a threaded seat for connecting a closing means or operations means to a metal plate, such as the wall of a drum, by making a hole in the plate and by drawing a cylindrical collar from the periphery around the hole approximately at a right angle to the plane of the plate, whereafter a thread is made in the part drawn from the plane of the plate wherein a thread is provided in the collar between of the plate and the end edge of the collar.
Crisci discloses a closure and container in which the closure has an axial flange which cooperates with the container to lock the closure in closed position. The closure also includes an annular recess accommodating a resilient seal for sealing against the container rim. The seal projects from the recess before assembly of the closure to the container.
The foregoing references generally address ways to solve or improve upon concerns of assembly, loosening or rotation of the closure and leakage of the container contents through or around the container. Admittedly, a number of secondary concerns are also addressed, such as a concern over closure distortion which is presented by the Dillon patent.
In Dillon, mention is made of the substantial lateral and radial forces associated with securing the closure into the container end. The concern expressed is in regard to the accuracy of closure threads and the ability of these threads to easily receive the threaded closure cap or plug. The Dillon approach to solving this concern is by means of a fairly complex structuring of the closure and container end. FIGS. 2-7 generally disclose this complexity and the point to understand with regard to the present invention is that Dillon does not utilize any portion of the container end as an internal, back-up support member or means for the closure.
The present invention also addresses a concern regarding distortion of the closure threads which may occur during the crimping operation or which may occur at other times when the closure is exposed to stresses such as exposure to high temperature during a paint-curing cycle. During the crimping operation, the synthetic material closure and its internal threads are exposed to substantial forces which tend to distort the threads and close-in the closure. The present invention achieves a reduction or conceivably elimination of such distortion and close-in by forming the raised boss of the container end with a downwardly extending axial portion that serves as back-up support for the closure not only during the crimping operation, but thereafter as the closure is subjected to stresses.
One option to the foregoing approach of the present invention is to use an extremely strong (high-strength) plastic wherein the material properties of that plastic based upon the size of the closure are sufficient to resist any close-in or distortion which might otherwise be caused by the crimping forces. In other words, if a material can be selected for the closure which will not yield to the level of forces created during the crimping operation, then the necessity for a back-up or support means is obviated. The drawback of this alternative approach is the higher material costs and thus a higher overall cost for the closure. By utilizing the container end boss as a back-up support, the plastic flange is supported by the metal of the drum end rather than relying solely on the compressive strength of the plastic flange to prevent close-in and thread distortion.
A higher-strength and more-expensive synthetic material for such a closure might include a nylon base material with 50 percent glass. A weaker, but less-expensive, synthetic material might include the same nylon base material with only 20 percent glass and 30 percent fillers.
One advantage of the present invention over prior devices which may incorporate a retaining ring as a securing means is the elimination of one component part. Elimination of such part results in not only a cost savings for the overall closure, but one less item which has to be ordered, stocked, assembled and replaced contributes to an improved product. An example of such a retaining ring concept wherein the ring has an interior portion for clamping the closure to the container boss is in U.S. Pat. No. 4,294,382 issued Oct. 13, 1981 to Summers et al.